Control system for internal combustion engine with catalyst for purifying exhaust gas

ABSTRACT

There is provided a control system for an internal combustion engine, which aim for early warm-up of catalyst and the engine in order to control a cooling loss and a heat radiation for cooling in such a way that the warm-up of the catalyst is carried out prior to the warm-up of the engine. That is, if the temperature of the catalyst is not greater than an activation temperature, there is carried out at least one of (1) retardation control of the ignition timing, (2) stopping control of a water pump for engine cooling water, (3) lowering control of the flow rate of the cooling water, but if the temperature of the catalyst is higher than the activation temperature, there is carried out at least one of control of the water pump in accordance with a temperature of the cooling water and control of retardation of the ignition timing, until the temperature of the cooling water reaches a warm-up temperature which is a normal operation temperature of the engine.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a control system for an internalcombustion engine, which incorporates catalyst for purifying exhaustgas, and in particular to a technology of fast activation of catalystfor purification of exhaust gas from an internal combustion engine, bycontrolling an engine cooling system or the like.

RELATED ART

[0002] As disclosed in, for example, JP-A-2000-34584 or JP-A-2000-45843,there have been well-known many technologies of inhibiting radiation ofheat from an engine to cooling water during a cold start in order toshorten the time of warm-up of the engine.

[0003] For example, the JP-A-2000-34584 discloses such a technology thatthe supply of cooling water is controlled in accordance with atemperature of a combustion chamber during operation of an engine so asto promote warm-up of the engine while the temperature of the wallsurface of a combustion chamber, which correlates to a quantity ofemergence of unburned HC components during a cold start is raised alongan optimum temperature rising characteristic. Specifically, the coolingwater is held in a reservoir tank when the wall temperature T of thecombustion chamber during engine operation is lower than a firstreference wall temperature T1, but the cooling water is displaced into acooling water jacket of the engine when it is higher than T1. After theabove-mentioned displacement of the cooling water is completed, thecirculation of the cooling water is started.

[0004] Further, the JP-A-2000-45843 discloses a technology of retardingthe ignition timing in an unwarmed-up condition so as to abruptlyincrease the exhaust temperature, exceeding a temperature of activationof catalyst for purification of exhaust gas so as to aim at promotingwarm-up of catalyst for purification of exhaust gas in order to allowthe catalyst to exhibit its purification characteristic in a shortperiod.

[0005] Neither such a control technology that the warm-up of an engineand the warm-up of catalyst for purification of exhaust gas areassociated with each other so as to carry out rational control, nor sucha technology of short-time warm-up of an internal combustion engine thatthe control of a cooling water system and the control of combustion arecombined with each other has not yet been built up in success.

BRIEF SUMMARY OF THE INVENTION

[0006] An object of the present invention is to provide a control systemfor an internal combustion engine, which can rationally control thewarm-up of the internal combustion engine and the warm-up of catalyst inthe order of priority during a cold start.

[0007] To the end, according to the first aspect of the presentinvention, there is provided a control system for an internal combustionengine incorporating catalyst for purifying exhaust gas therefrom, whichcontrols, during a cold start, a heat (cooling loss) transmitted fromcombustion gas to an engine block and a heat (heat radiation forcooling) transmitted from the engine block to engine cooling water, inorder to aim for early warm-up of the catalyst. Further, there isprovided a system for controlling the cooling loss and the heatradiation for cooling, so that the warm-up of the catalyst ispreferential to the warm-up of the internal combustion engine while theengine and the catalyst are warmed up in a short time.

[0008] The control of the cooling loss is made by controlling, forexample, the ignition timing while the control of the heat radiation forcooling is made by controlling the flow rate of cooling water throughthe intermediary of a water pump. That is, in such a case that thetemperature of the catalyst has not yet risen up to its activationtemperature, retardation control of the ignition timing is made so as todecrease the cooling loss, and as well, control is made such that theflow rate of cooling water is decreased to zero or a value smaller thana normal value so as to decrease the heat radiation for cooling.

[0009] The above-mentioned control is carried out being based at leastupon a temperature of engine cooling water or a temperature of thecatalyst. These temperatures are detected by a water temperature sensorand a catalyst temperature sensor. Further, the temperature of thecatalyst can be estimated or computed from an engine speed, a load, anignition timing, an EGR quantity, an intake air quantity and an intakeair temperature, a distance from the engine to the catalyst, the thermalcapacity (a number of cells or a volume) of the catalyst and the like.

[0010] Further, according to the first aspect of the invention, there isproposed a control system for controlling the engine in such a way thatthe heat radiation for cooling is minimized during activation control ofcatalyst until the catalyst is activated while the cooling loss ismaximized during control of warm-up of the engine until the engine iswarmed up after the activation of the catalyst.

[0011] With the above-mentioned control, the engine and the catalyst canbe warmed up in a short time, thereby it is possible to restrain theenvironmental contamination caused by exhaust gas and to enhance thefuel economy.

[0012] Further, according to the first aspect of the present invention,the ignition timing is retarded from the normal timing if the catalysttemperature is lower than its activation temperature while the ignitiontiming is advanced from the normal timing until the temperature ofcooling water rises up to a temperature at which the warm-up of theengine is completed, after the catalyst temperature rises up to itsactivation temperature.

[0013] With the configuration as stated above, not only the activationof the catalyst but also the warm-up of the engine can be promoted.Further, the provision of a knock sensor for detecting knocking of theinternal combustion engine is desirable so that the ignition timing isretarded when the knock sensor detects a knock during ignition timingcontrol, and further, the flow rate of the cooling water by the waterpump is increased in order to promote the warm-up of the internalcombustion engine in a sure and safe manner.

[0014] According to a second aspect of the present invention, there isprovided a control system for an internal combustion engine having aturbocharger for supercharging intake air in the internal combustionengine and a cooling passage for cooling the turbocharger, incorporatinga valve for controlling a flow rate of cooling water flowing through thecooling passage, in order to control the valve so as to reduce the flowrate of the cooling water flowing through the cooling passage if thetemperature of catalyst is not greater than an activation temperaturethereof, thereby it is possible to promote the activation of thecatalyst.

[0015] Further, according to a third aspect of the present invention,there is provided a control system for an internal combustion engineincluding a transmission for transmitting a power from the internalcombustion engine, an oil cooler for cooling oil lubricating thetransmission and a cooling passage for cooling the oil cooler,comprising a shut-off valve for shutting off the cooling passage,wherein the shut-off valve is controlled so as to stop the flow of thecooling water in the cooling passage if a temperature of catalyst is notgreater than its activation temperature, thereby it is possible topromote the activation of the catalyst.

[0016] Other objects, features and advantages of the invention willbecome apparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

[0017] The present invention will be hereinbelow detailed in the form ofpreferred embodiments with reference to the accompanying drawings inwhich:

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING

[0018]FIG. 1 is a block diagram of the present invention:

[0019]FIG. 2 is a conceptual diagram for explaining a cooling loss and aheat radiation for cooling in the present invention;

[0020]FIG. 3 is a diagram showing a relationship between an EGR quantityand a cooling loss;

[0021]FIG. 4 is a diagram showing a relationship between an ignitiontiming during combustion by spark ignition, and cooling loss;

[0022]FIG. 5 is a diagram showing a relationship between a fuelinjection timing and a cooling loss during combustion by compressionignition;

[0023]FIG. 6 is a diagram showing a relationship between a flow rate ofcooling water in an engine, and a heat radiation for cooling;

[0024]FIG. 7 is a diagram showing a relationship between a watertemperature of cooling water in an engine and a heat radiation forcooling;

[0025]FIG. 8 is a control flow-chart for a temperature controller;

[0026]FIG. 9 is a view illustrating an engine system in a firstembodiment of the present invention;

[0027]FIG. 10 is a diagram illustrating a control flow-chart in theembodiment shown in FIG. 9;

[0028]FIG. 11 is a view illustrating an example of a time-chart in anapplication of the present invention;

[0029]FIG. 12 is a diagram showing a relationship between a desiredvalue of the flow rate of cooling water, and a heat radiation forcooling;

[0030]FIG. 13 is a diagram showing a relationship between a desiredvalue of the ignition timing, and a cooling loss;

[0031]FIG. 14 is a view illustrating an engine system in a secondembodiment of the present invention;

[0032]FIG. 15 is a control flow-chart in the embodiment shown in FIG.14;

[0033]FIG. 16 is a time-chart during execuation of the control shown inFIG. 15;

[0034]FIG. 17 is a view illustrating an engine system in a thirdembodiment of the present invention;

[0035]FIG. 18 is a control-flow chart in part in the embodiment shown inFIG. 17; and

[0036]FIG. 19 is a time-chart during execution of the control shown inFIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0037] The present invention will be hereinbelow made of embodiments ofthe present invention with reference to the accompanying drawings.

[0038] Referring to FIG. 1 which is a block diagram illustrating acontrol system for an intern combustion engine, in accordance with anembodiment of the present invention, a temperature controller 101carries out temperature control of the engine and catalyst (which is aimat purifying exhaust gas from the engine) so as to aim for early warm-upof both engine and catalyst during a cold start of the engine.

[0039] Signals indicating a temperature of the catalyst, a temperatureof cooling water and knocking, which are detected by sensors, arereceived by the temperature controller 101 which therefore computes adesired heat radiation for cooling, and a desired cooling loss in orderto control an engine cooling system. The cooling loss and the heatradiation for cooling will be detailed after the configuration shown inFIG. 1 is briefly explained.

[0040] The desired heat radiation for cooling is delivered to a coolingsystem controller 102 while the desired cooling loss is delivered to anengine controller 103 for controlling the combustion of the engine.

[0041] Further, the cooling system controller 102 controls a water pumpin the engine cooling water passage, a flow passage control valve, aradiator and the like in accordance with the desired heat radiation forcooling so as to control the value of heat radiation for cooling.Meanwhile, the engine controller 103 controls intake and exhaust valves,a fuel injection valve an ignition unit, an EGR valve and the like inaccordance with the desired cooling loss so as to control the coolingloss.

[0042] The temperature controller 101, the cooling system controller 102and the engine controller 103 may be constituted by, for example, acontrol unit C.

[0043] The essential feature of the present invention is the provisionof the control of the cooling loss and the heat radiation for cooling inaccordance with at least either one of a temperature of the catalyst anda temperature of cooling water, and an object of the present inventionis to materialize both early activation of the catalyst and earlywarm-up of the internal combustion engine.

[0044] Explanation will be hereinbelow made of the cooling loss and theheat radiation for cooling in detail with reference to FIG. 2 whichshows the transmission of heat which is generated from a combustionchamber 1 in the engine and which is then transmitted to cooling water2.

[0045] The cooling loss in the present invention is a heat value withwhich a heat generated from the combustion gas in the combustion chamber(cylinder) 1 of the engine is transmitted to an engine block 3. Thecooling loss relates to an averaged temperature Ta and a temperature tothe engine block 2 during engine cycles (intake cycle, compressioncycle, expansion cycle and exhaust cycle) carried by a piston 4, and inparticular to those during a period from the compression cycle to theexhaust cycle. Thus, it is understood that the cooling losssignificantly relates to the combustion. As shown in FIG. 3 which shows,as an example, the relationship between an EGR (exhaust gasrecirculation) value and the cooling loss, an increase in the EGR valuecauses the averaged temperature Ta to lower since a possible maximumcombustion temperature is lowered. Thus, the cooling loss can becontrolled by adjusting the EGR value through the control of the EGRvalve and the intake and exhaust valves.

[0046] Further, the averaged temperature also relates to an ignitiontiming, and accordingly, the cooling loss can be controlled by theignition timing during combustion by spark ignition, as shown in FIG. 4,and it can be controlled by an injection timing during combustion bycompression ignition (Diesel combustion or combustion by premixself-ignition), as shown in FIG. 5.

[0047] Meanwhile, the heat radiation for cooling, concerned in thepresent invention, is a heat value transmitted from the engine block 3to the cooling water 2. The heat radiation for cooling mainly relates toa flow rate and a temperature of the cooling water 2.

[0048] Referring to FIG. 6 which shows an example of the relationshipbetween the flow rate of the cooling water and the heat radiation forcooling, the relationship between the flow rate and the heat radiationfor cooling, as shown in FIG. 6, exhibits, the higher the flow rate, thegreater the heat radiation for cooling. Further, referring to FIG. 7which shows a relationship between the temperature of the cooling waterand the heat radiation for cooling, if the temperature of the engineblock is constant, the lower the temperature of the cooling water, thegreater the heat radiation for cooling. Thus, the heat radiation forcooling can be controlled by a discharge quantity of the water pump orby a radiator for radiating a heat from the cooling water into theatmospheric air.

[0049] Further, another feature of the present invention, is theprovision of the control for the heat radiation for cooling and thecooling loss in accordance with a temperature of the catalyst and atemperature of the cooling water.

[0050]FIG. 8 shows a flow-chart as to the temperature controller 101.

[0051] Referring to FIG. 8, at step 801, outputs from a catalysttemperature sensor, a water temperature sensor and the like aretransmitted to the controller 101.

[0052] At step 802, the catalyst temperature is compared with a catalystactivation temperature at which the catalyst can purify exhaust gas, andif the catalyst temperature is not less than the catalyst activationtemperature, step 804 is carried out, but if it is false, step 803 iscarried out.

[0053] At step 803, a desired heat radiation for cooling is minimized.It is noted here that the minimum desired heat radiation for coolingcorresponds to a minimum value in a controllable range. Due to thisminimum control of the heat radiation for cooling, the heat valuetransmitted to the cooling water is decreased while the temperature ofexhaust gas is increased so as to enable early warm-up of the catalyst,that is, it is possible to fast raise the temperature of the catalyst upto the activation temperature in comparison with the conventional one. Aspecific example of the minimum control of the heat radiation forcooling will be described later.

[0054] At step 804, whether the temperature of engine cooling watercomes up to a warm-up temperature at which the engine can be efficientlyoperated as usual or not is determined, and if it is true, step 806 iscarried out, but if it is false, step 805 is carried out.

[0055] At step 805, the desired cooling loss is set to be maximum. As aresult, the heat value transmitted to the engine block is increased, andfurther, since the heat radiation for cooling is minimized, the enginecan be warmed up fast in comparison with a conventional one. The maximumcontrol of the heat radiation for cooling will be described later. It isnoted here that the maximum of the cooling loss corresponds to a maximumvalue in a controllable range.

[0056] At step 806, whether the water temperature is not lower than anoverheat temperature at which there would be a risk of occurrence ofseizure of the engine, or not is determined, and if it is true, step 805is carried out, but if it is false, step 807 is carried out. At step807, optimum fuel consumption control is carried out and the desiredcooling loss is minimized.

[0057] It is noted that the desired cooling loss is in a controllablerange, and it indicates a position of optimum spark advance (optimumspark ignition timing) as shown in FIG. 4 if the cooling loss iscontrolled only by the spark ignition timing. This optimum sparkignition timing enables the engine to operate with a high degree ofefficiency.

[0058] At step 808 at which control is made for an abnormal operation,that is, the desired heat radiation for cooling is maximized so as tocarry out cooling of the engine block by the cooling water at a maximumdegree in order to prevent occurrence of seizure of the engine.

[0059] Referring to FIGS. 9 to 12, a specific control example in thisembodiment will be explained.

[0060]FIG. 9 is a view which shows a configuration of the engine in thisembodiment.

[0061] In this example, a cooling system for an engine 5 is composed ofa cooling water circulation passage 6, a water pump 7 for controllingheat radiation for cooling in the cooling system, a water temperaturesensor 8 for measuring a temperature of cooling water, a radiator 9 forradiating heat from the cooling water into the atmospheric air, aradiator fan (which is not shown) for controlling the radiation of heatfrom the radiator into the atmospheric air, and a flow passagechange-over valve (thermostat) 10 for introducing cooling water.

[0062] Further, catalyst 12 (3 way catalyst) for purifying exhaust gasand a catalyst sensor 13 for detecting a temperature of the catalyst areincorporated in an exhaust pipe 11 of the engine. Further, there isprovided a knocking sensor 14 for detecting knocking of the engine.

[0063] Referring to a flow-chart shown in FIG. 10, explanation will behereinbelow made of control for early warm-up of both catalyst 12 andengine 5.

[0064] At step 1001, outputs from the catalyst temperature sensor 13,the water temperature sensor 8 and the knocking sensor 14 are read.

[0065] At step 1002, whether a value detected by the catalysttemperature sensor 13 is not less than the activation temperature of thecatalyst or not is determined, and if it is true, step 1004 is carriedout, if it is false, step 1003 is carried out.

[0066] At step 1003, the water pump 7 is stopped while the ignitiontiming is retarded in order to fast warm up the catalyst 12. As thewater pump 7 is stopped, the heat radiation for cooling to cooling waterbecomes minimum so as to aim at raising the temperature of the engine 5,and further, the temperature of exhaust gas from the engine is raisedthrough the control of retardation of the ignition timing. As a result,it is possible to aim for early warm-up of the catalyst. It is notedthat the retardation of the ignition timing may decrease the coolingloss, as shown in FIG. 4, but may not minimize the cooling loss.Although the cooling loss is minimized at a position where the ignitiontiming is optimum, but in-this case, since efficient combustion iscarried out, the temperature of exhaust gas may not be raised as is madethrough the control of retardation.

[0067] At step 1004, whether a value of engine cooling water detected bythe water sensor 8 reaches the warm-up temperature of the engine 5 ornot is determined, and if it is true, step 1006 is carried out, but ifit is false step 1005 is carried out.

[0068] At step 1005, in order to warm up the engine 5, the ignitiontiming is advanced so as to raise the temperature of the enginecylinder. At this time, through the control of the cooling system, thestop and the operation of the water pump 7 are repeated or the dischargerate of the pump 7 is controlled to be minimum although it is operated.

[0069] Through the circulation of cooling water at a small rate asmentioned above, it is possible to prevent occurrence of thermal stressin the engine block and knocking due to a hot spot in the enginecylinder.

[0070] At step 1006, it is determined that whether a value detected bythe water temperature sensor or an estimated value of the temperature ofthe engine is not less than an overheat temperature at which the seizureof the engine is expected, or not. If it is true, step 1008 is carriedout, but if it is false, step 1007 is carried out. At step 1007, controlfor minimizing the fuel consumption is carried out. Thus, the ignitionis controlled at an ignition timing with which the cooling loss isminimized, and the pump is controlled so that the temperature of coolingwater becomes not less than the warm-up temperature but not greater thanthe overheat temperature at which the seizure of the engine occurs.

[0071] It is noted that a temperature of the engine is estimated fromthe cooling loss and the heat radiation for cooling, and if the historyof temperature of the engine exhibits an increase while the engine loadis high, foreseeing control through which the flow rate of cooling waterincreases in advance may be carried out. In this foreseeing control, ifthe history of temperature of the engine exhibits a decrease while theengine load is low, the flow rate of cooling water is decreased inadvance, or the circulation of cooling water into the radiator may bestopped.

[0072] At step 1008, control upon overheating is carried out, that is,the flow rate of cooling water from the pump 7 and the output of theradiator are maximized so as to increase the heat radiation for coolingin order to prevent occurrence of seizure of the engine. Further, if thetemperature is not lowered within a predetermined time after theabove-mentioned controlled is carried out, the ignition timing isretarded so as to also decrease the cooling loss. Further, since theoverheating is caused by any abnormality in the cooling system includingthe radiator and the pump, a warning lamp is turned on for indication ofrequirement for a fault diagnosis.

[0073] As to the fault diagnosis, if, for example, a water temperatureis higher than an overheat temperature while the engine is operated atan idle speed, the radiator fan is operated being alternately changedover between a highest speed and a lowest speed (including a stop),every predetermined time. At this time, a fault diagnosis for theradiator can be made in accordance with a speed of the radiator fan anda variation in the output of the water temperature sensor. Specifically,a correlation between the speed of the radiator fan and a variation inthe output of the water temperature sensor is calculated, and if thethus calculated correlation is small, it can be determined that theradiator or the thermostat fails.

[0074] Similarly, by changing over the output of the pump everypredetermined time between a high output power and a low output power,it is possible to carry out a fault diagnosis of the pump in accordancewith a correlation between a variation in temperature of cooling waterand a control input to the pump. Specifically, a correlation between acontrol input of the pump and a variation in the output of the watertemperature sensor is calculated, and if this correlation is small, itcan be determined that the pump fails.

[0075] Referring to FIG. 11 which shows an example of a time-chart inthe case of execution of the warm-up control for both catalyst andengine, according to the present invention, during warm-up of thecatalyst until the temperature of the catalyst comes up to itsactivation temperature, the ignition timing is retarded, and the pump isstopped so as to set the flow rate to zero. During warm-up of the engineafter activation of the catalyst, the ignition timing is advanced, andif knocking is detected, the ignition timing is retarded while the flowrate of the pump is increased in order to prevent occurrence of abnormalcombustion.

[0076] After completion of the warm-up of the engine, the pump isoperated in a steady-state, and also the ignition timing is reset to anormal position.

[0077] Referring to FIG. 12 which shows control objectives of the flowrate in the control according to the present invention, cooling water isblocked until the warm-up of the catalyst is completed so as to minimizethe heat-radiation for cooling, and after completion of the warm-up ofthe catalyst, the flow rate of cooling water is controlled so as to below as possible as it can until the warm-up of the engine is completed.After the completion of the warm-up of the engine, the flow rate iscontrolled in accordance with a value of the heat radiation for cooling,thereby it is possible to optimumly materialize early warm-up of thecatalyst and the engine.

[0078] Further, referring to FIG. 13 which shows control objectives ofthe ignition timing in the control according to the present invention,optimum early warm-up can be materialized by retarding the ignitiontiming at one and the same engine speed during warm-up of the catalystbut by advancing the ignition timing up to a knocking critical valueduring warm-up of the engine after completion of the warm-up of thecatalyst, with respect to a normal ignition timing after completion ofthe warm-up. That is, if the ignition timing is retarded, after-burningis caused in exhaust gas discharged from the cylinder of the engine, andaccordingly, the temperature of the exhaust gas becomes higher, therebyit is possible to aim for early warm-up. At this time, although thecooling loss is small, it is, more or less, greater than that with thenormal ignition timing (efficiency drive) after completion of thewarm-up.

[0079] Referring to FIGS. 14 to 16, explanation will be hereinbelow madeof a second embodiment of the present invention.

[0080] Referring to FIG. 14 which shows the configuration of an enginein the second embodiment, this configuration is the same as that shownin FIG. 9, except that there are provided a turbocharger 15 forsupercharging the intake air in an exhaust pipe 11, a cooling passage 6a for cooling the turbocharger 15, a bypass passage 6 b bypassing thecooling passage 6 a, and a bypass valve 16 for blocking the flow in thebypass flow passage 6 a.

[0081] The cooling passage 6 a and the bypass passage 6 b arealternately connected to the engine cooling passage 6 through switchingcontrol of the bypass valve 16.

[0082] Referring to FIG. 15 which is a control flow-chart of the bypassvalve 16 in this embodiment, at step 1501, a value from the catalysttemperature sensor 13 is read, and at step 1502, whether the temperatureof the catalyst is greater than an activation temperature thereof or notis determined. If it is true, step 1504, the bypass valve 16 is closed(default). Meanwhile, it is false, at step 1503, the bypass valve 16 isopened so as to bypass cooling water flowing through the turbocharger 15during warm-up of the catalyst.

[0083] Referring to FIG. 16 which shows a time-chart in the case ofexecution of the control according to the present invention, duringwarm-up of the catalyst, by opening the bypass valve 16, the lowering ofthe temperature of exhaust gas, which is caused when the exhaust gaspasses through the turbocharger, can be minimized, thereby it ispossible to fast warm-up the catalyst. It is noted that even duringwarm-up of the engine, if a relief valve for bypassing the flow ofexhaust gas flowing into a turbo-turbine is closed, no cooling isrequired for the turbocharger, and accordingly, the bypass valve 16 maybe opened.

[0084] Referring to FIG. 17 which shows a third embodiment of thepresent invention, the configuration of this embodiment is the same asthat shown in FIG. 9, except that there are provided an oil cooler 18for cooling a transmission 17, a cooling passage 6 c for cooling the oilcooler 18 and a shut-of valve 19 for blocking the cooling passage 6 c.

[0085] Referring to FIG. 18 which shows an control flow-chart of theshut-off valve 19 in this embodiment, at step 1801, a value from thecatalyst temperature sensor 13 is read, and at step 1802, whether thecatalyst temperature is not less than its activation temperature or notis determined. If it is true, at step 1804, the shut-off valve 19 isopened, but if it is false, at step 1803, the shut-off valve 19 isclosed.

[0086] Referring to FIG. 19 which shows a time-chart in the case ofexecution of the control according to the present invention, duringwarm-up of the catalyst, the shut-off valve 19 is closed so as toshut-off the flow of cooling water flowing through the oil cooler 18 inorder to decrease the heat radiation for cooling, and as a result, theexhaust temperature rises up, thereby it is possible to fast warm up thecatalyst.

[0087] According to the present invention, by controlling the coolingsystem in accordance with a catalyst temperature, the catalyst can befast activated. Further, in combination of the control of the coolingsystem for the engine or the like with the control of the engine, thewarm-up of the catalyst can be made prior to the warm-up of the enginewhile aiming at warming up both the catalyst and the engine. Thus, withthe application of the present invention, it is possible to reduceemission of exhaust gas due to early activation of the catalyst, and toimprove the fuel consumption due to early warm-up of the internalcombustion engine.

[0088] It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

What is claimed is:
 1. A control system for an internal combustionengine incorporating catalyst for purifying exhaust gas from the engine,characterized in that a heat transmitted from combustion gas to anengine block (cooling loss) and a heat transmitted from the engine blockto cooling water (heat radiation for cooling), are controlled to effectearly warm-up of the catalyst during a cold start of the engine.
 2. Acontrol system for an internal combustion engine as set forth in claim1, wherein the cooling loss and the heat radiation for cooling arecontrolled in such a way that the warm-up of the catalyst is carried outprior to the warm-up of the engine while aiming for early warm of bothcatalyst and engine during a cold start of the engine.
 3. A controlsystem for an internal combustion engine as set forth in claim 1 or 2,wherein the control of the cooling loss is carried out by controlling anignition timing, and the control of the heat radiation for cooling iscarried out by controlling a flow rate of engine cooling water by meansof a water pump, and if a temperature of the catalyst has not yet reachits activation temperature, the ignition timing is retarded undercontrol so as to decrease the cooling loss while a flow rate of theengine cooling water is set to be zero or smaller than a normal flowrate so as to decrease the heat radiation for cooling.
 4. A controlsystem for an internal combustion engine as set forth in any one ofclaim 1 to 3, wherein the cooling loss and the heat radiation forcooling are controlled in accordance with at least either a temperatureof engine cooling water or a temperature of the catalyst.
 5. A controlsystem for an internal combustion engine as set forth in any one ofclaims 1 to 4, wherein the heat radiation for cooling is controlled soas to be minimum until the temperature of the catalyst comes up to theactivation temperature.
 6. A control system as set forth in any one ofclaims 1 to 5, the cooling loss is controlled to be maximum until theinternal combustion engine is warmed up after the temperature of thecatalyst reaches the activation temperature.
 7. A control system for aninternal combustion engine comprising cooling water for cooling theengine, a circulation passage for the cooling water, a water pump forcontrolling a flow rate of the cooling water, and catalyst for purifyingexhaust gas from the engine, characterized in that the water pump iscontrolled in accordance with a temperature of the catalyst.
 8. Acontrol system for an internal combustion engine as set forth in claim7, wherein the water pump is stopped under control if the temperature ofthe catalyst is not greater than an activation temperature at which thecatalyst can purify the exhaust gas, and the water pump is controlled inaccordance with a temperature of the cooling water after the temperatureof the catalyst reaches the activation temperature.
 9. A control systemfor an internal combustion engine incorporating cooling water forcooling the engine, a circulation passage for the cooling water, a waterpump for controlling a flow rate of the cooling water and catalyst forpurifying exhaust gas from the engine, characterized in that if atemperature of the catalyst is not greater than an activationtemperature, control is made in such a way that at least either (1) anignition timing is retarded from the normal one, (2) the water pump isstopped, or (3) the flow rate of the cooling water becomes less than thenormal one, if the temperature of the catalyst is higher than theactivation temperature, control is made in such a way that at leasteither (5) the water pump is controlled in accordance with a temperatureof the cooling water, or (6) the ignition timing is advanced from thenormal one, until the temperature of the cooling water reaches a warm-uptemperature which is a normal operation temperature of the engine.
 10. Acontrol system for an internal combustion engine as set forth in claim9, further comprising a knocking sensor for detecting knocking of theinternal combustion engine, wherein when knocking is detected, theignition timing is retarded under control, and the water pump iscontrolled so as to increase the flow rate of the cooling water.
 11. Acontrol system for an internal combustion engine incorporating aturbocharger for supercharging intake air in the engine, a coolingpassage for cooling the turbocharger and catalyst for purifying exhaustgas, characterized by a valve for controlling a flow rate of coolingwater flowing through the cooling passage, wherein the valve iscontrolled so as to decrease the flow rate of the cooling water flowingthrough the cooling passage if the temperature of the catalyst is notgreater than an activation temperature.
 12. A control system for aninternal combustion engine incorporating a transmission for transmittinga power from the engine, an oil cooler for cooling oil which lubricatesthe transmission, a cooling passage for cooling the oil cooler, andcatalyst for purifying exhaust gas, characterized by a shut-off valvefor blocking the cooling passage, wherein the shut-off valve iscontrolled so as to stop the flow of the cooling water in the coolingpassage if a temperature of the catalyst is not greater than anactivation temperature.